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#45199 11/21/04 01:58 PM
Joined: Sep 2004
Posts: 86
Mounting a Cantex FSS plastic box on a 4X4 cedar post. The box, of course, has four mountings which are located on the sides of the box. The mounting ears are not quite covered by the cedar post so we would be required to make a bracket large enough to be behind the mounting ears or put in screws at an angle to hit the cedar post. Instead we drilled two holes on the inside of the box and used sealing washers and #10 screws into the cedar post. I felt this was a very secure and water tight installation but the inspector turned it down, stating that UL does not state that mounting the boxes that way was an option. I felt this was ludicrous and a total lack of common sense but I am open to discussion on why I could be wrong. I hope to contact UL and get their opinion on this installation but would like to hear from all of you inspectors out there as to your experience regarding mounting outdoor receptacle boxes. If the customer had installed 4X6 posts like I requested we wouldn't be having this discussion but not allowing this installation with the sealing washers sounds a bit rediculous to me. Any UL people out there?
Thanks Guys in advance for your great reponses to all questions.

Joined: Feb 2003
Posts: 169
While your installation is probably adequate I can't find anything to argue your point but common sense and experience. Metal bell boxes have always had the option of using the ears that come with the box, or punching out small mounting knock outs on the back of the box.

Joined: Nov 2002
Posts: 794
Likes: 3
The issue may be that one of the hot wires might, thru its insulation failing, make the mounting screw hot. With a metal box the screw would be grounded (as the box would be grounded) and the breaker would trip. With a plastic box the screw would stay hot, and if the wood was at all conductive (maybe damp) create a hazard. I don't think any screw heads are permitted inside plastic boxes.

Joined: Feb 2002
Posts: 375
Gluing the box to the post (3M 5200) would work.

A waterproof caulk rather than washers would work.

Joined: Feb 2002
Posts: 2,233

As an AHJ I would probably let that job go as is. As Rus M said, most metal FS boxes always allowed you to punch out the hole to mount the box to a post, etc. If you want to be 100% correct, then yes, you would have to contact UL to make sure that it woud meet the UL standard.

Joined: Jun 2004
Posts: 92
I think you made a good faith effort. Using the flimsy plastic wings would be physically less secure which is probably more important than absolute waterproof integrity.
The interior will get moist from condensation anyway.
However the inspector is literally right and, in this case, the boss. Maybe a little chuck of 6" X 6" plywood would be in order.

Joined: Sep 2004
Posts: 167
I can tell you UL's opinion or answer on this. "The box has not been investigated for mounting in this manner."

yeah, the inspector was absolutely right in his statement.

My opinion, well I would have to see it. Sounds like you could find a way to seal it adequately. If your inspector compromises with you, then it would be prudent to follow instructions next time, unless you clear it advance.

so smooze him. Tell him you understand he is right and that you've learned something. Could we please work out a compromise to apply to this installation only?

Washers and caulk would be good. Plywood won't hold up.

Larry LeVoir
City of Irvine, CA
Joined: May 2004
Posts: 697
I never drill holes inside the box. Whenever I see them mounted this way they are wet and corroded from leaking.


Joined: Jan 2003
Posts: 1,429
LK Offline
We use the Cantex FS Box with the mounting tabs in vert position, not all supply houses stock them, for some reason they stock the boxes, with the tab on the sides.

[This message has been edited by LK (edited 11-21-2004).]

Joined: Sep 2004
Posts: 86
Are you saying that cantex makes the boxes with verticle mountings? That would be the answer. Nobody mentioned that. I'll have to get the catalog and see if I could order them.
Thank You
You don't get prior permission from an inspector for something that seems to be a common sense approach. I'm interested in seeing if UL specifically states that a bubble cover can be mounted on this box or have we been just taking that for granted since the screw holes match. This situation has me very interested in getting educated on what UL really covers on each of their products. I am always glad to go along with the local inspector if he can back up his position with the proper article or UL listing. I just can not tolerate inspectors that make us change things according to their personnal desires which we were not able to figure into the quote beforehand. If I get a good answer from UL regarding mountings I will pass on anything of interest.
Thanks for the replies.

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